Surface covered structure and surface covering therefor



SURFACE COVERED STRUCTURE AND SURFACE COVERING THEREFOR Filed Jan. 11, 1944 Def 28, 1948 G. K. BIEMESDERFER, JR 2,457,299

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GEORGE Kalsmesdxznnzrfi,JR.A

Patented Dec. 28, 1948 SURFACE COVERED STRUCTURE AND SUR- FACE COVERING THEREFOR George K. Biemesderfer, Jr., Lancaster, Pa., as-

signor to Armstrong Cork Company, Lancaster, Pa., a corporation of Pennsylvania Application January 11, 1944, Serial No. 517,858

This invention relates to a covering for surfaces such as floors. wall-s, work space areas, and lthe like where there is a hazard involved in any spark discharge. The invention also is concerned with structures such as floors, walls, Work table tops, and similar areas having a sparkproof working or wearing surface. The invention will find usefulness in hospital operating rooms, powder drying houses, laboratories, Work tables and similar work spaces in fuse-loading plants, powder feed hoppers, and, in fact, in any area where an explosion is likely to occur through a spark discharge.

It is believed that the invention will find particular usefulness as a covering for floors in hospital operating rooms for there it is necessary to have a iioor which is highly conductive of electri- Y cal current which will not spark when struck by a metallic object, such -as an instrument which might be accidentally dropped on the floor, and in which it is desirable to have a floor which has good light reflecting characteristics, a pleasing appearance, and one which will not be affected by soap, ,alcohol, or other solvents which might come into contact with the covering.

It is well known that in hospital operating rooms where ether is being administered to patients, explosions have occurred due to spark discharges of static electricity. Such explosions are serious and when the ether in the patients iungs is ignited, the explosion which results ruptures the lungs, causing death.

Conductive floor coverings have been prepared andin recent years, -a large demand has been created for such coverings in army and navy hospitals, shell loading plants, powder drying rooms,

and other areas. The material most commonly used for this purpose is a -tile which comprises resinous binder and graphite and may or may not include suitable fillers. With such coverings it is dii'ncult to obtain unusual decorative effects for the tile must of necessity be relatively darkcolored because of the nature of the conducting material which is incorporated therein.

It is an object of my invention to provide a covering which may be formed essentially of decorative elements which may be light-colored and have good light reflecting characteristics, the covering being conductive of electrical current throughout a substantial portion of its wearing or working surface so that a person or object moving over the surface will not accumulate a charge of static electricity sumcient to result in .aspu'k discharge and any electrical charge car- 2 Claims. (Cl. 175-264) 2 ried by the person or object will be immediately dissipated.

Another object of my invention is to provide a surf-ace covered structure which may have a decorative, light reflecting surface and will have sufllcient current conducting surface area that spark discharge from persons or objects moving thereover will not be possible.

I pref-er to form the covering as a preformed sheet, much the same as linoleum. This makes possible the use of regular inlaying equipment available in the linoleum industry, provides for the formation of sheets of great length with a continuous or unitary conducting grid work or the like. With such equipment, it is possible to form a continuous sheet of conducting plastic composition, such as the conductive linoleum composition comprising 625 parts linoleum -eement, 4 parts pigment (carbon black), 100 parts fresh linoleum scrap, 100 parts finely divided cork particles, and 325 parts graphite. Such material has an electrical resistance of less than 250,000 ohms when measured in accordance with Federal specification where the resistance is measured between the ground and a five-pound electrode in direct contact with five square inches of the conductive material on a floor. Portions are died and removed from the sheet to receive the decorative inlays and the resulting grid work of plastic composition is laid onto the backing, such vas the asphalt saturated felt now commonly used in linoleum manufacture. The inlays in one or more colors, in plain or variegated effects, are then inserted in the openings in the grid work to form a continuous upper surface. All of this may be accomplished on an automatic inlaying machine, such as the rotary inlaylng machine used by linoleum manufacturers.

In another embodiment of my invention, the surface is covered with decorative elements which are separated by strips of conductive plastic composition, the pattern being laid up in the same manner as tile is laid. In such event, it is desirable to connect the conductive elements ltogether electrically rather than rely on good edgeto-edge surface contact. This may be accomplished by the use of a. conductive adhesive into which the strips are pressed into firm engagement, or by the use of a similar adhesive at the line of juncture where the various conducting strips abut, or the adhesive may be used in both places. Another method of securing good electricai contact at the joints is t-o heat-fuse them by melting a portion of the strips adjacent the junc- 3, ture line with a heated iron and dowing the melted composition into the Joints.

In order that my invention may be more readily understood, I will describe the same in connection with the attached drawing in which:

Figure 1 is a plan view illustrating a preferred door covering;

Figure 2 is a sectional view -taken on the line II-II of Figure l Figure 3 is a sectional view showing the i'loory covering adhesively secured to a base;

Figure 4 is a plan view showing a modined covered structure in which the elements are laid as tiles;

Figure 5 is a sectional view on the line V-V of Figure 4; and

Figure 6 is a sectional view similar to Figure 5 but showing a modified Joint arrangement.

Referring to Figures 1 and 2, the covering consists of a backing 2 which in the embodiment illustrated is made of felt. The felt is preferably a rag felt saturated with a moisture-resistant substance such as asphalt, flux oil, drying oil, lacquer, or the like. In place of felt, other fibrous material may be used, including burlap, cotton sheeting, or other foundation materials such as those commonly used in the manufacture of linoleum.

It is preferred that the conductive portion of the covering be formed from a single sheet of conductive composition to thus insure that there be perfect electrical communication throughout all parts of the conductive area. 'Ihis may be accomplished by forming a sheet of conductive composition on a calender in the manner customarily practiced in linoleum manufacture. Portions of this sheet are then .died out and the remaining composition inv the form of a lcontinuous grid. as illustrated at i in Figure 1, is laid on the backing 2. Inv the embodiment shown in Figures l, 2, and 3, the grid is died out with 3" x 3" openings and the grid work is about 55" wide. Inlays l are inserted in the openings in the grid work and as will be seen from an examination of Figure 2, all of the openings are filled to present a continuous upper surface B, constituting the exposed working or wearing surface ofthe' covering. The inlays l may belaid automatically on a rotary inlaying machine, well known in the linoleum industry,

and after the entire area of backing has been covered with the grid work and inlays, the material is fed throughs calender which consolidates the grid I and the inlays I onto the backing 2. The material may then be cured by hanging in a heated curing stove for the required time to effect the proper hardness and so-called maturity to the composition.

The inlays may be formed of any composition and where the covering is. designed for" hospital use, the inlays are preferably formed of light-colored linoleum composition vhaving good light reflection characteristics. As'shown in Figure l, the inlays may be marbelized, but they may be plain, mottled or striated, as desired.V

The grid constitutes a substantial portion of the exposed upper surface of the covering and its extent should be at least such that a person walking over the door will normally tread on a portion at least of the grid work at each step. With 3" x 3" inlays'and 1A" interliners, this is accomplished. The spacing of the inlays and disposition of the grid will depend to a considerable extent uponthe design desired. While a square tile deisn with interliners simulatl? mortar joints has been shown, it is understood that other designs are possible and attractive modernistic designs can be made using strips of conductive composition with a relatively few inf ter-connecting conductive strips between the major elements of the design.

In Figure'fi, the covering is illustrated as applied to a concrete base B which may constitute a sub-floor, for example. A layer of adhesive 1 is used and since the covering is in the form of a preformed sheet, installation is relatively simple and may be rapidly accomplished. Where a burlap or cotton fabric backing is employed rather'than the felt shown in Figure 3, it may be desirable to apply first a layer of deadening felt, but this will depend upon the nature of the 'base and the service to which the covering will be put.

Figures 4 and 5 illustrate a modified form of my invention wherein the surface covered structure includes'an exposed working or wearing 'surface formed of individual tile-like elements ap"- plied to the base without an intermediate backing. In other words, in the embodiment shown in Figures 4 and 5, the material is laid generally in the form of tiles which are adhesively secured to the base. In laying up such a structure as the floor of Figures 4 and 5, the base 8 is coated with an adhesive s and the longitudinal strip IIl is installed. The strip III is of conductive composition, such as the composition of the tile disclosed in the Martin application, above referred to. Next, the inter-connecting strip II is laid and then the inlay I2 and the strip I3. The operation is repeated along the longitudinal strip I0 until the row is completed. Next, the longittudinal strip Il is installed and the operation is repeated with alternate inter-connecting strips I5 and inlays I8 until the entire area is covered. Preferably, the adhesive 9 is made of a conductive material such as asphalt containing graphite particles so that when the longitudinal strips I0, Il and so forth and the inter-connecting strips II, Il, I5 and so forth are bonded to the 'base 8 by the adhesive 9, each of the strips is electrically connected to the conductivefadhesive and through the adhesive to each other' to.form an electrically inter-connected conductive grid.

In some instances, it may be desirable to elec,- trically connect the strips at the upper surface, particularly in powder drying houses and the like, and this may be accomplished by heat welding at the lines I1 where the inter-connecting strips, as the one I8, joins the longitudinal strips I0 and I4. As will'be noted in'Figure 5, the welded joints are formed fromV composition melted from the strip I0 andthe adjacent interconnecting strip Ig and the longitudinal strip Il and inter-connecting strip I8. The same joining is effected at each joint. 1., In another modification, the same eil-ect may be accomplished by applying relatively thin. lms of conductive adhesive I9 at the jointbetween the longitudinal strips I0 and I4 andthe interconnecting strip I8 as shown in Figure 6. This is preferably done by coating the edges of the inter-connecting strips immediately prior to installation and pressing thesame ,into firm engagement with the previously laid longitudinal strip.

When the longitudinal and inter-connecting strips are joined as in Figures 5 andi and also where they are integral as in Figure' l, the 4grid work acts electrically asa condenser. Aswill' be observed from Figure 3, thegrid work I 'is elec'- trleally insulated from ground by the felt backing 2, the adhesive 1 and the base 6, leaving the conductive portion of the covering to act as a condenser. When the covered area is large, as in an average operating room for example, the grid work will possess a high capacitance. The voltage or difference in potential is directly proportional to the static charge divided by the capacitance and with a' high capacitance it is almost impossible to build up a large enough voltage to cause a spark. The conductive portion 'of the covering is so highly conductive that it almost instantaneously reaches an equal potential at all portions. There will always be a slow bleeding of any charge on the floor through the backing, base, and atmosphere to ground so that no charge of any consequence will build up in the covering.

In some instances, it may be desirable to ground the grid work and this is shown in Figure 6 where the conductive adhesive 9 is connected to ground, indicated at 20.

The present invention makes possible the creation of attractive floors, walls, and other surface covered structures, which may possess good light reflection characteristics and which at the same time will not spark or permit the building up or discharge of static electricity in such manner as to cause a spark. It also makes possible the manufacture of a exible covering on automatic inlaying equipment, utilizing a major portion of regular linoleum composition inlays with a minor amount of dark-colored conductive composition, substantial, however, in the sense that an object or person moving over the covering will frequently engage a conductive portion of the exposed working or wearing surface.

While I have illustrated and described certain preferred embodiments of my invention, it will be understood that the same may be otherwise embodied and practiced within the scope oi' the following claims.

l. A ilexible surface covering of the type capable of being rolled for shipment and installation comprising a non-conductive, flexible backing, flexible strips of electrically conductive plastic sheet material overlying and secured to the backing in closed spaced relationship, said strips being electrically connected into a current conducting grid, and inlays of flexible composition in sheet form secured to the backing and filling the openings in said covering and terminating in the plane of the upper surface of the grid, said grid, inlays and backing being consolidated into a unitary final structure capable of being rolled for shipment.

2. A ilexible hard surface covering of the linoleum type capable of being rolled comprising a fibrous backing, an open grid work formed from a single sheet of electrical current conducting linoleum composition secured to the backing and inlays of non-conductive lineloum composition in sheet form secured to the backing and disposed within said openings and terminating in a common plane with said grid work, said grid, inlays and backing being consolidated into a unitary final structure capable of being rolled for shipment.

GEORGE K. BIEMESDERFER, Jn.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 794,672 Gutwasser July 11, 1905 1,632,497 Noel June 14, 1927 1,661,037 Gammeter Feb. 28, 1928 1,852,696 Chaee Apr. 5, 1932 1,854,512 Heppes Apr. 19, 1932 2,108,759 Turman Feb. 15, 1938 2,114,710 Holcomb Apr. 19, 1938 2,229,742 Kauffman Jan. 28, 1941 2,261,072 Monahan Oct. 28, 1941 2,287,766 Davis June 30, 1942 2,298,983 Stabe Oct. 13, 1942 2,302,003 Cadwell et al Nov. 17, 1942 2,323,461 Donelson July 6, 1943 2,327,029 Donelson et al. Aug. 17, 1943 2,341,360 Bulgin --Feb. 8, 1944 

